1. Field of the Invention
The present invention relates to a device for the thermal deburring of workpieces, comprising at least one deburring chamber and a feed means for introducing a fuel gas mixture into the deburring chamber.
2. Description of the Related Art
In installations for the thermal deburring of workpieces, random material removal takes place during which the entire workpiece is subjected to a heat shock. Corners and edges are preferably removed, since these locations, with a large surface and small volume, absorb an especially large amount of heat and are thus oxidized and burned. The heat shock is achieved by burning off a fuel gas mixture which preferably comprises a fuel gas, such as, for example, hydrogen, natural gas or methane, and an oxidizing gas, such as, in particular, oxygen.
To carry out this method, at least one workpiece is inserted into the deburring chamber, for example with a “closing plate”, such that that a closed-off combustion chamber is formed with the deburring chamber. The fuel gas mixture is then introduced into this closed deburring chamber. The fuel gas mixture can be fed in such a way that the individual gas constituents are introduced separately into the deburring chamber; mixed feeding of the fuel gas constituents, at least in a last section of the feed process, is preferred in this case. In the process, depending on the size of the deburring chamber or the number of workpieces, very high positive pressures can be realized, for example up to 50 bar.
By corresponding ignition means, for example a spark plug, which can be installed in the region of the combustion chamber or else in a feed passage through to the deburring chamber, the fuel gas mixture is then ignited, such that the heat shock described at the beginning is generated.
After this thermal deburring method has been carried out and in particular in the event of abnormal occurrences, if, for example, no ignition is effected, the gas volume located at positive pressure in the combustion chamber then has to be released again. To this end, it was to begin with normal practice to simply open the deburring chamber, that is to say, for example, to remove the closing plate from the deburring chamber. However, it has been found with this method that very pronounced contamination could occur in the entire region between closing plate and deburring chamber, and this contamination may possibly also result in abrasive wear of the seal provided between the deburring chamber and the closing plate.
A further development is described in EP 1 232 822 A1. It is proposed there that a quick-acting vent valve be assigned to the deburring chamber, via which quick-acting vent valve the gas present in the deburring chamber can be released. This also provides, for example, the possibility of cleaning the deburring oxides and residues via a filter.
However, it has to be taken into account that, in cases where there is still an ignitable or explosive fuel gas mixture in the combustion chamber, such rapid outflow via such a quick-acting vent valve may possibly be dangerous. In this case, it should in particular be borne in mind that with some ignitable fuel gas mixtures even a low energy feed is sufficient to possibly trigger an ignition. For this reason, in the case of such quick-acting vent valves, the release is regularly realized in such a way that the flow velocities through the central valve are kept very low in order to avoid ignition of the fuel gas mixture as a result of gas friction for example. If the fact that such quick-acting vent valves are provided with a very small diameter is taken into account, the slow release of the explosive fuel gas mixture from the deburring chamber, in particular if the latter has a large volume, results in long downtimes of the installation.
Proceeding therefrom, the object of the invention is to at least partly solve the problems described with reference to the prior art. In particular, a device and a method are to be specified which make possible short venting times and at the same time rule out the risk of self-ignition.